Wooden containers capable of being assembled on wooden palates can be made to suit the shipping load. The wooden container can be reinforced to suit the load, using blocking & bracing. A wooden container of standard dimension 1219 mm (48 inches)×1016 mm (40 inches)×1016 mm (40 inches) typically weighs 158-181 kg (350-400 lb). These wooden containers are neither insulated nor able to absorb appreciable shock. As a result products shipped with wooden containers are more vulnerable to damage en route. The wooden containers are also not washable and thus products shipped using wooden containers can be contaminated in situ. The wooden containers are not knock down, thereby restricting the ability to re-use the wooden container.
Other deleterious factors associated with wooden shipping containers include injuries caused by wood splinters and nails to people who handle the wooden container. Additionally, disposal of the wooden container at the end of its useful life has negative consequences for the environment.
The adoption of International Standardized Phytosanitary Monitoring (ISPM)-15 for wood packaging material (WPM) requires treatment of kiln drying of all wood in shipping containers. The United States in cooperation with Mexico and Canada began enforcement of the ISPM 15 standard on Sep. 16, 2005. The North American Plant Protection Organization (NAPPO) strategy for enhanced enforcement has been conducted in three phases. Phase 1, Sep. 16, 2005 through Jan. 31, 2006, implemented an informed Compliance via account managers and notices posted in connection with cargo that contains noncompliant WPM. Phase 2, Feb. 1, 2006 through Jul. 4, 2006, introduced rejection of violative containers and pallets through re-exportation from North America. Informed compliance via account managers and notices posted in cargo with other types of non-compliant WPM remained in force. On Jul. 5, 2006, phase 3 enforcement took effect, involving full enforcement on all articles of regulated WPM entering North America. Non-compliant Regulated WPM are not allowed to enter the United States. The adoption of ISPM-15 reflects the growing concern among nations about wood shipping products enabling the importation of wood-boring insects, including the Asian Long horned Beetle, the Asian Cerambycid Beetle, the Pine Wood Nematode, the Pine Wilt Nematode and the Anoplophora Glapripwnnis.
Thus the wooden dunnage platform has become unattractive for the international shipment of products. In addition, the wooden shipping container does not protect the shipment from accidental damage or theft as a result of accidental or intentional damage to the shipping container. The construction of wooden containers allows viewing of the products being shipped, which can allow a thief to target particular products. Any wood furring strips used to seal surfaces or cracks in wooden containers and thereby conceal the identity of the product being shipped must also meet the ISPM-15 requirements.
Food and other perishable produce being shipped can suffer from deleterious storage effects arising as a result of the uncontrolled atmosphere associated with the wooden container. Further, the wooden surface is not a sanitary surface, since it can harbor insects as well as mould and bacteria deposits.
Plastic shipping containers, constructed with plastic are known, see U.S. Pat. No. 3,915,089 to Nania, and U.S. Pat. No. 6,216,608 to Woods et al. These hard shell plastic shipping containers use no wood products and are very strong. However, they are relatively heavy (48″×40″×40″ is typically 45-272 kg (100-600 lb) depending on the container type, e.g., a frame with minimal siding versus a container with structural integrity) and are expensive to manufacture. In general, because one piece molding is employed with plastic shipping containers, they cannot be ‘knocked-down’ or otherwise disassembled prior to return to the shipping point of origin or other appropriate destination. As a result these plastic shipping containers have a 1:1 shipping to return ratio. That is the return of the empty container requires just as much space as the original container shipment with the product.
Some shipping container manufacturers have attempted to produce a more sanitary surface by combining foam with wooden surfaces. These containers still suffer a number of disadvantages including their weight, the presence of wood requiring treatment, and their ease of entry for a thief. Further, coating the wood with foam adds the additional disadvantage that the container cannot be easily knocked down or disassembled for return to the shipping point of origin or other appropriate destination.
Thermoplastic molding is used to create a wide variety of useful articles. In general, the process of thermoplastic molding involves heating a thermoplastic material to its glass transition temperature, at which point the material become pliable, molding the pliable thermoplastic into the shape of a desired article and allowing the article to cool. Once a thermoplastic material cools to a temperature beneath the range of its glass transition temperature the material become significantly less pliable and maintains its new shape. A number of processes have been developed for shaping thermoplastics including single and twin sheet thermoforming.
Thermoplastics can be used to laminate various articles including load-bearing structures. U.S. Pat. No. 5,833,796 to Matich, which is herein incorporated by reference in its entirety, involves applying thermoplastic sheets to a preformed rigid structure. The structural component is essentially rigid and a thermoplastic skin is applied to either one or both sides of the structural component. U.S. Pat. No. 5,833,796 to Dummett, which is herein incorporated by reference in its entirety, discloses applying thermoplastic sheets to a preformed rigid structure for manufacturing dunnage platforms.
The manufacture of articles by twin sheet thermoplastic molding often involves the use of complimentary male and female molding tools. In one common methodology a thin sheet of thermoplastic material is heated until it is pliable, and positioned adjacent to a male mold. The thermoplastic sheet is then moved relative to the tool's surface until the sheet assumes the same shape as the surface of the tool. A second sheet of thermoplastic material is heated until it becomes pliable. The heated second sheet is then centered over the cavity of a female molding tool and moved relative to the female tool molding until the interior portion of the second sheet substantially conforms to the interior shape of the female tool.
Vacuum-assist molding uses a vacuum to help draw heated thermoplastic sheets into contact with the surface of the tools. Irrespective of how they are formed, after the two thermoplastic sheets have taken on the shapes of the male and female molds, the edges of the sheets are pressed together and welded to form a single article. U.S. Pat. No. 5,641,524 to Rush et al., which is hereby incorporated by reference in its entirety, discloses vacuum-assist thermoplastic molding.
An alternative to vacuum molding is plug-assist molding. In plug-assist molding, a rigid tool is used to push a heated sheet at least partly into the cavity of a second tool with a surface shape complimentary to the shape of the first tool. U.S. Pat. No. 6,379,606 to Chun et al., and U.S. Pat. No. 5,641,524 to Rush et al., both of which are hereby incorporated by reference their entirety, describe plug-assist molding. U.S. Patent Application 026,0344 to Bearse et al., which is hereby incorporated by reference in its entirety, describes using a compressible core as a plug in the plug-assist molding process. The compressible core member used becomes a part of the manufactured article and helps to strengthen and stabilize the article. The compressible member, as a part of the manufactured article, continues to resist compression. The expansive force exerted by the core member trying to expand against the constraining force exerted by the shell strengthens the bond between the shell and the core.